Regression (bisected): Lots of wakeups when using battery
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From: Jaime Velasco Juan on 30 Jul 2010 17:50 Hi, testing 2.6.35-rc5 I noticed that when my laptop is on battery, there are bursts of wakeups (they seem random, but usually happens once each 5 sec. or so; they cause some audible noise). If the laptop is plugged it behaves well. In single user mode, there are usually 2 wakeups/sec with the system idle, but on battery an with the bug, it goes to more than 100 w/s. Bisection points to: commit 3310d4d38fbc514e7b18bd3b1eea8effdd63b5aa Author: Peter Zijlstra <peterz(a)infradead.org> Date: Thu Jun 17 18:02:37 2010 +0200 nohz: Fix nohz ratelimit Chris Wedgwood reports that 39c0cbe (sched: Rate-limit nohz) causes a serial console regression, unresponsiveness, and indeed it does. The reason is that the nohz code is skipped even when the tick was already stopped before the nohz_ratelimit(cpu) condition changed. Move the nohz_ratelimit() check to the other conditions which prevent long idle sleeps. Reverting said commit seems to fix the issue. Regards -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Mike Galbraith on 31 Jul 2010 00:10
(corrects cc) On Fri, 2010-07-30 at 22:45 +0100, Jaime Velasco Juan wrote: > Hi, testing 2.6.35-rc5 I noticed that when my laptop is on battery, > there are bursts of wakeups (they seem random, but usually happens once > each 5 sec. or so; they cause some audible noise). If the laptop is plugged > it behaves well. In single user mode, there are usually 2 wakeups/sec with > the system idle, but on battery an with the bug, it goes to more than 100 w/s. > > Bisection points to: > > commit 3310d4d38fbc514e7b18bd3b1eea8effdd63b5aa > Author: Peter Zijlstra <peterz(a)infradead.org> > Date: Thu Jun 17 18:02:37 2010 +0200 > > nohz: Fix nohz ratelimit > > Chris Wedgwood reports that 39c0cbe (sched: Rate-limit nohz) causes a > serial console regression, unresponsiveness, and indeed it does. The > reason is that the nohz code is skipped even when the tick was already > stopped before the nohz_ratelimit(cpu) condition changed. > > Move the nohz_ratelimit() check to the other conditions which prevent > long idle sleeps. > > Reverting said commit seems to fix the issue. And if you revert that, using a serial console becomes.. unpleasant. The whole ratelimit nohz thing has been dropped for now. It's a nice little optimization for high frequency switchers on an underutilized box, but has caused more irritation than it's worth. -Mike -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |